Type II Cepheids: Evidence for Na-O anticorrelation for BL Her type stars?

V. Kovtyukh, I. Yegorova, S. Andrievsky, S. Korotin, I. Saviane, B. Lemasle, F. Chekhonadskikh, S. Belik

Resultado de la investigación: Contribución a una revistaArtículorevisión exhaustiva

5 Citas (Scopus)


The chemical composition of 28 Population II Cepheids and one RR Lyrae variable has been studied using high-resolution spectra. The chemical composition of W Vir variable stars (with periods longer than 8 d) is typical for the halo and thick disc stars. However, the chemical composition of BL Her variables (with periods of 0.8-4 d) is drastically different, although it does not differ essentially from that of the stars belonging to globular clusters. In particular, the sodium overabundance ([Na/Fe] ≈ 0.4) is reported for most of these stars, and the Na-O anticorrelation is also possible. The evolutionary tracks for BL Her variables (with a progenitor mass value of 0.8 solar masses) indicate that mostly helium-overabundant stars (Y = 0.30-0.35) can fall into the instability strip region. We suppose that it is the helium overabundance that accounts not only for the existence of BL Her variable stars but also for the observed abnormalities in the chemical composition of this small group of pulsating variables.

Idioma originalInglés
Páginas (desde-hasta)2276-2285
Número de páginas10
PublicaciónMonthly Notices of the Royal Astronomical Society
EstadoPublicada - 21 jun 2018

Áreas temáticas de ASJC Scopus

  • Astronomía y astrofísica
  • Ciencias planetarias y espacial


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